A friction drive device for an omni-directional vehicle that can freely move about on a floor is known, for instance, from Japanese patent No. 3820239. This device comprises a main wheel including an annular member and a plurality of driven rollers rotatably supported along the outer circumference of the annular member, and a plurality of drive rollers engaging the outer circumferential surfaces of the driven rollers at the outer circumferential surfaces thereof so that the rotation of the drive rollers may be frictionally transmitted to the driven rollers.
The applicant of this application previously proposed a friction drive device for an omni-directional vehicle that comprises a base frame, a first moveable member and a second moveable member each moveably supported by the base frame, a first drive unit and a second drive unit configured to actuate the first moveable member and second moveable member, respectively, a plurality of first free rollers arranged on the first moveable member along the direction of movement of the first moveable member, each rotatable around an axial center line thereof, and a plurality of second free rollers arranged on the second moveable member along the direction of movement of the second moveable member, each rotatable around an axial center line thereof, wherein, as at least one of the first and second moveable members moves, one of the first free rollers engages the corresponding one of the second free rollers at the outer circumferential surfaces thereof with the central axial lines thereof disposed in a non-parallel relationship so that power may be transmitted from the second free rollers to the first free rollers engaging an object to be driven. See WO2008/132778.
Furthermore, the applicant of this application previously proposed a friction drive device for an omni-directional vehicle that comprises a main wheel (first moveable member) including an annular member and a plurality of driven rollers (first free rollers) arranged circumferentially along the annular member so as to be each rotatable around the tangential line of the annular member at the position of the driven roller, a pair of rotatable members (second rotatable members) on either side of the main wheel, each rotatable around the central axial line thereof, a plurality of drive rollers (second free rollers) each mounted on each rotatable member so as to engage the outer circumferential surfaces of the corresponding driven rollers at the outer circumferential surface thereof with the axial line of each drive roller disposed in non-parallel relationship with respect to the axial line of the corresponding driven roller so that the rotation of the rotatable members may be transmitted to the main wheel via the frictional engagement between the outer circumferential surfaces of the drive rollers and outer circumferential surfaces of the driven rollers. See WO2008/132779.